Congrats on starting out at that high a level. I'm in my 3rd yr and still do mostly 7th, 8th, MS and Freshman games. I am getting some JV and V now though.
Along with what's already been said - relax on the court, have fun and enjoy what your doing, always hustle, be confident, know the proper hand/arm signals - practice them and use them correctly, officiate as many games as possible no matter what level (but, avoid mens rec league
), don't listen/hear the players/coaches/fans whining, trust your partner, concentrate on your primary, never throw your partner under the bus, have a thick skin, lurk and learn on this Forum, and very importantly (from a former player/coach) READ THE RULE BOOKS. As players/coaches you only thought you knew the rules..... I'm sure others will chime in with more.
Good luck and let us know how it goes.